Royal Mail is to recruit more than 21,000 seasonal staff to help sort the Christmas post.

The company estimated 18,000 of the posts will be in England, 2,000 in Scotland, 700 in Wales and 400 in Northern Ireland.

The temporary jobs would be available between early November and January 2014 and support Royal Mail's permanent 124,000 postmen and women who sort and deliver the mail all year round.

Royal Mail's managing director of operations and modernisation, Mark Higson, said: "Christmas is the busiest time of the year for Royal Mail and we plan all year round to help ensure we deliver the best possible service to our customers.

"Every Christmas, we make a substantial financial commitment in additional resources to handle the festive mailbag, including the recruitment of thousands of temporary workers."

The annual drive for festive posties is held against a backdrop of unrest in the ranks, as the Communication Workers Union (CWU) prepares a vote on national strikes over the Government's plans to privatise the Royal Mail.

The CWU, which announced the ballot on Monday, said it believed industrial action was "inevitable" without compromise from the company on issues including pay, jobs, pensions and the impact of any sell-off.

The result of the ballot will be revealed in early October and the first strike could be held on October 10 if there is a yes vote.

A lack of progress on settling the row could potentially lead to a protracted dispute spilling over into the festive season, Royal Mail's most profitable period.

The union's move is a major challenge to the planned privatisation, which ministers are expected to press ahead with in the coming months that would see staff secure free shares worth an estimated £2,000 each.

The CWU says the arrangement offers its members little in terms of guarantees over their future.